In a future update it would be helpfull if the web address for online subtitles can be filled in by the user, I believe now its fixed to opensubtitle.org. Opensubtitle.org ended their api but the one at opensubtitle.com can be used, unless the address cab be entered to login. Even so, one could have a private subtitle database to use, if that web address can be entered.
Under \settings\player options\online subtitles\signup\